Diagnosing device of signal status in measurement and control by measuring means and control means

Abstract

This aims to provide a diagnosing device for detecting the measurements of an electric current, a voltage and a resistance by a temperature/moisture or pressure sensor or a signal state in control means, precisely with a simple circuit constitution, for diagnosing the soundness of a circuit while simplifying a power source circuit, to suppress the cost more than the conventional circuit having no diagnosing function, and for diagnosing the signal status in the measurement or control by a measuring means or a control means. An alternating voltage generating means containing a pulse-wave voltage and an alternating current is connected with the primary side of a transformer, and a driven member such as the measuring means for any of varying electric current, voltage and resistance is connected with the secondary side. The change in the primary-side current, which is caused with the electric power fed through an insulating transformer by the action of the driven member connected with the secondary side, is measured so that the signal status in the measuring or control means is diagnosed according to the measurement result.

1. A device for diagnosing signal status in measurement and control by a driven object, the device comprising:
 a voltage generating means for generating a pulse voltage and an alternating voltage, 
 a measuring means of which a current, a voltage, or a resistance varies is changed, or a driven object which converts a change of state of a controlling object into a change of a current, a voltage, or a resistance, 
 a rectifying circuit, and 
 a transformer having a primary side connected to the voltage generating means, and a secondary side connected to the measuring means or the driven object through the rectifying circuit, 
 wherein the transformer is an insulation transformer of which the primary side is insulated from the secondary side, 
 a primary winding is provided with an intermediate tap, 
 a current measuring means is connected to the intermediate tap to measure a current in the primary side of the transformer caused by a current flow in the driven object connected to the secondary side via the rectifying circuit, and 
 a detection of a change in the current, the voltage, or the resistance of the driven object and an evaluation of soundness of a circuit are performed based on a measurement result of the current measuring means. 
 
     
     
       2. A device for diagnosing signal status in measurement and control according to  claim 1 , wherein
 said driven object is a measuring transmitter which converts the measurement result into an analog current value and outputs the analog current value, 
 the detection of the current, the voltage, or the resistance in the driven object and the evaluation of soundness of the circuit are performed by measuring a change in a current on the intermediate tap in the primary side of the transformer caused by a current applied to said measuring transmitter via said rectifying circuit by said current measuring means. 
 
     
     
       3. A device for diagnosing signal status in measurement and control according to  claim 1 , wherein
 said driven object is a sensor which outputs the measurement result as a voltage or a change in resistance and which has a signal conversion circuit for converting output of the sensor into a current value, and 
 the detection of the current, the voltage, or the resistance in the driven object and the evaluation of soundness of the circuit are performed by measuring a change in a current on the intermediate tap in the primary side of the transformer caused by a current which flows from the rectified circuit to said signal conversion circuit by said current measuring means. 
 
     
     
       4. A device for diagnosing signal status in measurement and control according to  claim 1 , wherein
 said driven object is a control means which switches on/off in accordance with ambient conditions including pressure, temperature, and humidity, 
 the control means has a means for switching resistance values in accordance with ON/OFF state of said control means, and, 
 the device further comprises a diagnosing means which detects a change in a current on the intermediate tap in the primary side of the transformer caused by a current which flows from the rectifying circuit to the resistance by said current measuring means and which detects whether said control means is switched-on or -off and diagnoses circuit soundness.